It was not until long after his grandmother, Sophie, had died, that Michael Jacobs was eventually permitted to read the lengthy and passionate letters that his grandfather Bethel had written her from nine thousand miles away. In these letters, Jacobs discovered a remarkable story of hardship, deprivation and enduring love. His grandfather's work on the railway through the Andes was exhausting and desperately lonely. He had little in common with his fellow workers and became consumed by a mounting despondency, from which only his love for Sophie could save him. But, as the months and years of separation passed, the world in which Sophie was blossoming appeared more and more remote from his own.

Michael Jacobs' journey back through time takes him from a rain-swept Hull churchyard to desolate Antofagasta in Chile and to the former silver capital of Potosí. Climbing through ghostly, lunar-like scenery towards the snow-capped summits of the Andes, he follows the route of his grandfather's railway - across giant rocky plateaux, through terrifyingly steep gorges and valleys of tropical lushness, and past grim mining townships buffeted by winds, rain and snow - to reveal an extraordinary love story.